EBM 2024: Lecture 1
Definition and Importance of Evidence-Based Medicine
Austin Meyer, MD, PhD, MS, MPH, MS
2024-08-30
Definition and Importance of Evidence-Based Medicine (EBM)
What is Evidence-Based Medicine?
- Integration of:
- Best research evidence
- Clinical expertise
- Patient values and preferences
Importance of EBM in Clinical Practice
- Improves patient outcomes
- Enhances quality of care
- Promotes efficient use of resources
- Keeps practitioners updated with latest research
The EBM Process
- Ask - Formulate clinical question
- Acquire - Gather relevant evidence
- Appraise - Evaluate evidence quality
- Apply - Integrate with patient care
- Assess - Evaluate outcomes
The EBM Process: Ask
Formulate a clear clinical question - PICO
The EBM Process: Acquire
- Search for the best available evidence
- Utilize databases like PubMed, Cochrane Library
- Cochrane
The EBM Process: Appraise
- Critically evaluate the evidence
- Assess validity, relevance, and applicability
- There are lots of tools for this:
The EBM Process: Apply
- Integrate evidence with clinical expertise
- Consider patient preferences and circumstances
The EBM Process: Assess
- Evaluate the outcome of the decision
- Reflect on the process and identify areas for improvement
Levels of Evidence
Question 1
A 7-year-old boy with a history of recurrent asthma exacerbations presents to the clinic. His parents are concerned about the long-term effects of inhaled corticosteroids and have read conflicting information online. They ask whether continuing the medication is the best option for their child. As a clinician using Evidence-Based Medicine (EBM), what is the first step you should take to address their concerns?
Explanation: The first step in the EBM process is to formulate a clear clinical question using the PICO (Patient/Population, Intervention, Comparison, Outcome) framework, which will guide the search for the best available evidence.
Question 2
A pediatric resident is reviewing a recent study that suggests a new treatment for pediatric eczema. The study is a randomized controlled trial (RCT) with a large sample size and demonstrates statistically significant results. According to the principles of Evidence-Based Medicine (EBM), which of the following best describes the importance of this study’s findings?
Explanation: In EBM, randomized controlled trials (RCTs) represent a high level of evidence. However, the findings should be integrated with the clinician’s expertise and the patient’s values and preferences before being applied in practice.
Question 3
Which of the following best exemplifies the integration of patient values and preferences in the practice of Evidence-Based Medicine (EBM) for a pediatric patient?
Explanation: EBM involves not only the integration of the best available research evidence and clinical expertise but also the incorporation of the patient’s values and preferences into the decision-making process. Collaborating with the family to choose the most appropriate course of action exemplifies this integration.
Research Methods Overview
Types of Clinical Research
Experimental vs. Observational Studies
- Experimental Studies
- Interventions are actively manipulated.
- Example: Randomized Controlled Trials (RCTs).
- Observational Studies
- No intervention; researchers observe outcomes.
- Example: Cohort studies, Case-control studies.
Study Designs
- Randomized Controlled Trials (RCTs)
- Gold standard for assessing causality.
- Random assignment to intervention or control.
- Cohort Studies
- Observational; follows a group over time.
- Can be prospective or retrospective.
- Case-Control Studies
- Compares individuals with a condition (cases) to those without (controls).
- Efficient for studying rare diseases.
- Cross-Sectional Studies
- Snapshot at a single point in time.
- Useful for prevalence studies.
Randomized Controlled Trials (RCTs)
Gold Standard for Causality
Cohort Studies
Observational Study Design
Case-Control Studies
Retrospective Study Design
Cross-Sectional Studies
Snapshot in Time
Understanding study type and its analysis
Understanding study type and its analysis
Critical Appraisal of Research Articles
Questions to ask for appraisal
- Study Design: Was the study design appropriate for the research question? (e.g., RCT, cohort, case-control)
- Sample Size: Is the sample size sufficient to detect a meaningful difference or effect? (i.e. is there sufficient power)
- Do we have a sense for what is a reasonable power?
- Blinding and Randomization: Were the participants and researchers adequately blinded, and was the randomization process robust?
- Outcome Measures: Are the outcome measures valid, reliable, and clinically relevant?
Assessing Bias in Research
What happens when the questions are not well answered
- Selection Bias: Are the participants selected in a way that may skew the results?
- Selection bias occurs when the participants included in a study are not representative of the target population, leading to results that may not be generalizable.
- Information Bias: Is there a systematic error in how data is collected or classified?
- Information bias occurs when there is a systematic error in the way data is collected, measured, or recorded in a study, leading to inaccuracies in the data that affect the study’s outcomes.
- Confounding: Are there other variables that could influence the results, not accounted for?
- Confounding occurs when an extraneous variable (a confounder) is associated with both the exposure and the outcome, leading to a spurious association between them.
Relevance to Clinical Practice
Prior questions were about internal validity (i.e. was the study conducted well)
- External Validity: Can the results of the study be applied beyond the patients in the study?
- Applicability: Can the study results be applied to your specific patient/population?
- Patient Values and Preferences: Does the evidence align with your patients’ needs, circumstances, and preferences?
Question 4
A pediatric researcher is planning a study to investigate the effectiveness of a new vaccine in preventing a common childhood infection. The researcher randomly assigns participants to either receive the new vaccine or a placebo, with both the participants and the clinicians blinded to the assignment. After a follow-up period, the incidence of the infection is compared between the two groups. Of the following, the BEST description of the study design used in this research is:
Explanation: A Randomized Controlled Trial (RCT) is the gold standard for evaluating the effectiveness of an intervention. Participants are randomly assigned to either the intervention or control group, and both participants and clinicians are blinded to the assignments to minimize bias.
Question 5
In a study assessing the relationship between breastfeeding and the development of allergies, researchers follow a group of infants from birth until 5 years of age. The researchers document the breastfeeding status of the infants and monitor them for the development of allergies during this period. Which of the following BEST describes the study design?
Explanation: A Cohort Study follows a group of individuals over time to observe how specific exposures (e.g., breastfeeding) affect the development of outcomes (e.g., allergies). This prospective study design is ideal for studying the natural history of diseases.
Question 6
When critically appraising a research article, a pediatric resident identifies that the study has a small sample size, potentially leading to low statistical power. Which of the following is the MOST appropriate concern related to low statistical power in this context?
Explanation: Low statistical power increases the risk of a Type II error, which occurs when a study fails to detect a true effect or difference. This means that there may be a real association or difference, but the study might not have enough power to demonstrate it due to the small sample size.
Applications to Clinical Practice
Role of Clinical Guidelines in Pediatrics
Introduction to Clinical Guidelines
- Definition: Clinical guidelines are systematically developed statements that assist clinicians and patients in making decisions about appropriate healthcare for specific clinical circumstances.
- Purpose: They aim to improve the quality of care by providing evidence-based recommendations.
- Structure: Virtually all guidelines begin with a systematic review of the literature.
Meta-Analyses (Part 1)
Overview and Key Concepts
- What is a Meta-Analysis?
- Meta-analysis is a statistical technique that combines the results of multiple studies to produce a single estimate of the overall effect.
- Effect Size and Models:
- Effect Size: A measure of the strength of the relationship between variables across studies (e.g., odds ratio, relative risk, mean difference).
- Fixed-Effect Model: Assumes that all studies estimate the same effect size; variability is due to random error.
- Random-Effects Model: Assumes that effect sizes vary across studies due to real differences; accounts for between-study variability.
Meta-Analyses (Part 2)
Advanced Techniques and Interpretation
- Forest Plots:
- Visual representation of individual study results and the overall pooled estimate.
- Each study is represented as a line, with the size of the marker indicating the weight of the study.
- Heterogeneity Assessment:
- I² Statistic: Measures the proportion of variability in effect estimates due to heterogeneity rather than chance.
- Cochran’s Q Test: Statistical test for heterogeneity; significant results indicate the presence of heterogeneity.
- Publication Bias Assessment:
- Funnel Plots: Scatterplot of study effect sizes against sample size to detect asymmetry, which may indicate publication bias.
Interactive Funnel Plot
Interpretting Funnel Plots
:::
Interpretting Forest Plots
:::
Systematic Reviews (Part 1)
Overview and Process
- What is a Systematic Review?
- A systematic review is a structured approach to reviewing the literature, aiming to answer a specific research question by synthesizing all relevant studies.
- Key Steps in Conducting a Systematic Review:
- Formulate Research Question: Use PICO (Population, Intervention, Comparison, Outcome) framework to define the scope.
- Search Strategy: Conduct comprehensive searches in multiple databases like PubMed, Cochrane, and Embase.
- Study Selection: Apply inclusion and exclusion criteria to identify relevant studies.
- Data Extraction: Systematically collect data from selected studies.
Systematic Reviews (Part 2)
Quality Assessment and Bias
- Critical Appraisal of Studies:
- Risk of Bias: Evaluate potential biases in the included studies using tools like the Cochrane Risk of Bias tool.
- Quality Assessment: Assess the quality of evidence using frameworks like GRADE (Grading of Recommendations Assessment, Development, and Evaluation).
- Synthesizing Evidence:
- Narrative Synthesis: Summarize the findings from studies qualitatively.
- Statistical Synthesis: If appropriate, use meta-analysis to quantitatively combine data.
- Common Biases in Systematic Reviews:
- Publication Bias: Studies with positive results are more likely to be published.
- Selection Bias: Inconsistent inclusion criteria across studies can affect outcomes.
Systematic Reviews (Part 3)
Example of a Bias Assessment by Cochrane
Question 7
You are reviewing a meta-analysis that includes a funnel plot to assess for publication bias. The plot shows a noticeable asymmetry with smaller studies tending to report larger effect sizes. Which of the following is the MOST likely explanation for this finding?
Explanation: Funnel plot asymmetry with smaller studies reporting larger effect sizes is commonly due to publication bias, where smaller studies with positive results are more likely to be published. Other explanations like heterogeneity and small study effects could play a role, but publication bias is the most likely cause of this pattern.
Question 8
A meta-analysis is performed to evaluate the effectiveness of a new vaccine in preventing childhood infections. Which of the following best describes the role of a meta-analysis in this context?
Explanation: A meta-analysis combines the results of multiple studies to provide a more precise estimate of a treatment’s effectiveness, increasing the statistical power and generalizability of the findings.
Question 9
When conducting a systematic review, a pediatric researcher follows a structured methodology to identify and appraise studies. Which of the following BEST represents a key step in the systematic review process?
Explanation: One of the first steps in conducting a systematic review is formulating a research question using the PICO (Population, Intervention, Comparison, Outcome) framework, which guides the literature search and study selection process.
Summary
Summary of Lecture 1: Evidence-Based Medicine
Key Takeaways
- Definition of EBM:
- Evidence-Based Medicine (EBM) integrates the best available research evidence, clinical expertise, and patient values to guide clinical decision-making.
- Research Methods Overview:
- Understanding the differences between study designs such as Randomized Controlled Trials (RCTs), Cohort Studies, and Case-Control Studies is crucial for interpreting research.
- Critical Appraisal:
- Critical appraisal of research articles includes evaluating the study methodology, assessing bias, and determining the relevance to clinical practice.
- Role of Clinical Guidelines:
- Clinical guidelines are developed based on systematic reviews and meta-analyses, synthesizing the best available evidence to improve the quality of care in pediatrics.
- Systematic Reviews & Meta-Analyses:
- Systematic reviews provide a structured approach to evaluating all available evidence, while meta-analyses combine results from multiple studies to generate more precise estimates of treatment effects.